The invention relates to a constant velocity joint in the form of a fixed joint with the following characteristics: an outer joint part which comprises a longitudinal axis and a first side S1 and a second side S2 arranged to as to be axially opposite one another, and which is provided with outer ball tracks; an inner joint part which comprises a longitudinal axis and attaching means for a shaft pointing to an aperture of the outer joint part, and which is provided with inner ball tracks; the outer ball tracks and the inner ball tracks form pairs of tracks with one another; the pairs of tracks each accommodate a torque transmitting ball; an annular ball cage is positioned between the outer joint part and the inner joint part and comprises circumferentially distributed cage windows which each accommodate at least one of the torque transmitting balls; the centers of the balls are held by the cage in a joint center plane and, when the joint is articulated, they are guided onto the angle-bisecting plane between the longitudinal axes.
Because of the way in which the ball tracks of the pairs of tracks in the outer joint part and inner joint part extend, fixed joints in the form of UF joints (undercut-free joints) feature a large radial ball movement when the balls in an articulated joint move to and fro along the ball tracks during a rotation of the joint while the ball tracks of the pairs of tracks—with reference to their starting position—are periodically articulated relative to one another on both sides by the joint articulation angle. The radial ball movement determines the minimum cage thickness of the ball cage, because during their entire radial movement during a rotation of the joint, the balls have to be guided within the cage windows, i.e. they must remain in contact with the circumferential guiding faces of the cage windows.
A large cage thickness necessarily reduces the degree of envelopment of the balls by the ball tracks, if seen in a cross-sectional view through the joint, because an increasing cage thickness leads to a reduction in the track depth of the outer ball tracks and inner ball tracks. A reduction in the track depth and a resulting reduction in the degree of ball envelopment lead to a decrease in the torque transmitting capacity of the joint.
U.S. Publication No. 2004/0116192 proposes constant velocity fixed joints wherein the opening angle α between tangents at balls in contact points with the ball tracks in the joint center plane when the joint is in the aligned condition with coinciding longitudinal axes, opens from the aperture end to the attaching end. There are given different track shapes which also include approximately S-shaped track center lines with a turning point in the outer joint part and in the inner joint part. The track center lines are defined as the path of the centers of the balls in the ball tracks. The strength of the outer joint part is to be increased with the help of the opposed orientation of said opening angle α—as compared to the UF joints—when the joint is in the aligned condition.
It is the object of the present invention to propose a fixed joint of the above-mentioned type whose torque transmitting capacity is increased further.